A NEW ONE-DIMENSIONAL PLATINUM SYSTEM CONSISTING OF CARBOXYLATE-BRIDGED CIS-DIAMMINEPLATINUM DIMERS

With the aim of developing new 1D platinum chain solids having infinit e Pt-Pt bonds, several carboxylate-bridged cis-diammineplatinum dimers have been prepared and structurally characterized. For a dimer doubly bridged with acetates, five different salts [Pt-2(NH3)(4)(mu-CH3CO2)( 2)]X-2. nH(2)O (X-2, n = (ClO4)(2), 2, 1; (NO3)(2), 1, 2; (BF4)(2), 4, 3; (PF6)(2), 2, 4; (SiF6), 4, 5) have been prepared. The crystal stru cture of 5 has revealed that an infinite dimer chain [Pt-2(NH3)(4)(mu- CH3CO2)(2)](n)(2n+) can be given as a result of hydrogen bond formatio n between the ammines and the oxygen atoms of acetates, demonstrating our prediction that the N2O2 coordination sphere may serve as a hydrog en-bonding moiety to assist formation of an infinite dimer chain. An a symmetric dimer bridged by both acetate and hydroxide ligands, [Pt-2(N H3)(4)(mu-CH3CO2)(mu-OH)](SiF6) (6), has also been isolated as a bypro duct of 5, and a similar 1D framework, [Pt-2(NH3)(4)(mu-CH3CO2)(mu-OH) ](n)(2n+), has been characterized by X-ray diffraction. In addition, s ome glycolate-bridged analogues of similar frameworks have been synthe sized and characterized: [Pt-2(NH3)(4)(mu-CH2(OH)CO2)(2)](SiF6). 4H(2) O (7), [Pt-2(NH3)(4)(mu-CH2-(OH)CO2)(2)] (ClO4)(2). H2O (8), and [Pt-2 (NH3)(4)(mu-CH2(OH)CO2)(mu-OH)](NO3)(2) (9) To obtain partially oxidiz ed systems, benzoate derivatives have been selected as bridging ligand s. Although a benzoate system gave dark blue solids ascribable to mixe d-valence Pt(2.25+) compounds, a crystallographically analyzed complex has turned out to be a double complex involving both a Pt(II) monomer and a dinuclear Pt(II) complex, [Pt-2(NH3)(4)(mu-C6H5CO2)(2)](2)(SiF6 ) (BF4)(2).[cis-Pt(NH3)(2)(C6H5CO2)(2)]. 3H(2)O (10). Nevertheless, ou r final efforts in this work have revealed that a p-hydroxybenzoate sy stem, [Pt(2.25+)(2)(NH3)(4)(mu-p-C6H4(OH) CO2)(2)](2)X-5. nH(2)O (X-5, n = (SO4)(2.25)(p-C6H4(OH)CO2)(0.5), 5, 12a; (PF6)(2)(SO4)(p-C6H4(OH) CO2), 6, 12b; (PF6)(2)(NO3)(2)(p-C6H4(OH)CO2), 7, 12c), may be suited to achieve a 1D platinum blue system. The compounds display a blue chr omophore at 630 nm ascribable to the Pt(2.25+)(4) species. Moreover, t he compounds have been judged to be diamagnetic, and therefore the S = 1/2 spins derived from the Pt(2.25+)(4) units must be diamagnetically coupled in the solid state, suggesting that the repeating unit should be expressed as [Pt(2.25+)(8)](n) (n is undetermined).